Zvyozdochka, part of the Unified Shipbuilding Corporation, that specialises in repairs and recycling of nuclear submarines, said it had signed a contract with the Indian Defence Ministry in 2010 to carry out maintenance and upgrade the submarine. The craft arrived there in August.
The submarine, which exploded after a fire on board and sank in a Mumbai dockyard early today in which 18 personnel, including three officers, may have been killed, was upgraded and it sailed to Mumbai in January, 2013.
The Severodvinsk-based shipyard said a modern Club-S missile system was installed on the submarine together with more than 10 Indian and foreign systems, including the Ushus hydro-acoustic system and the CCS-MK-2 communication system.
"The coolant system has been modernised; a Porpoise radar has been installed and other works have been carried out to enhance the submarine's combat capability and safe operation," Russian news agency Itar-Tass quoted a Zvyozdochka official as saying.
The Sindhurakshak was built by the Admiralteiskiye Verfi shipyard in St Petersburg in 1995. Meanwhile, seven Russian specialists, who had worked on the submarine earlier were reported to be "safe and sound".
"All the seven Russian specialists - five Zvyozdochka employees and two from partner companies who had serviced the submarine are safe and sound. They were in a hotel when the accident occurred," spokeswoman for Zvyozdochka, Sherbinina said.
In June last, the submarine was floated out after the staples phase of repairs. In November-December, the submarine successfully completed performance trials and the tests of torpedo and missile armaments at firing ranges in the White Sea.
It has modernised five diesel electric submarines for the Indian Navy since 1997. The companies are continuing repairs and upgrade of a similar vessel in Visakhapatnam, the report said.